d-cyco-1

I have been having a inconsistent miss around 5500RPM. I checked the fuel pressure and this is what I got.

Idle with vacum 36-37 psi
Idle w/o vacum 41-42 psi

Full throttle with vacum the pressure jumps to 42psi and then drops to 30 psi and stays there.

So I am thinking that the pump can't keep up any more. Any other suggestions would be appreciated.

my94blackz

coil

d-cyco-1

Coil??? How do you figure? Don't you think 30 psi is low fuel pressure for wide open throttle?

Injuneer

At WOT, the fuel pressure should stay within 1 or 2psi of the "no vacuum" pressure. 30psi is way too low. Changed the filter?

d-cyco-1

I have changed the filter once but it was a couple of years ago. I don't drive the car much and it only has 18k on it. I figure after heads/cam and 30# injectors the car is demanding more fuel. Plus I have t=endency to runn the car with a quaaaaarter take of gas that is not good for the pump either.

HBHRacing

when you trun the key on and prime the system a few times without the engine running does the pressure hold or bleed down? if your filter is new and the pressure is holding steady then yeah sounds like week pump not keeping up under heavy load. if the pressure is bleeding down could still be fuel pump IE check valve, a bad injector, regulator etc

d-cyco-1

I think it was holding pressure pretty good. With the key turned on it was around 41psi. After about and hour it had dropped down to about 20psi. Isn't the check valve located where the pump is?